1. Field of the Invention
The present invention relates to a catalytic converter and a manufacturing method thereof. More specifically, the present invention relates to a catalytic converter capable of effectively utilizing a catalyst component supported thereon, and to a manufacturing method of the catalytic converter.
2. Description of the Related Art
Heretofore, in a gasoline engine, technologies for exhaust gas purification have been advanced following strict regulation for exhaust gas, and harmful substances contained in the exhaust gas have been surely being reduced. However, since a diesel engine has particularity to emit harmful components in a form of particulates, legal regulation for the harmful components and technical development for purification thereof have been delayed in comparison with those of the gasoline engine.
However, with regard to the particulates emitted from an internal combustion engine of an automobile, and particularly, from the diesel engine, a particle diameter of most thereof is 1 μm or less, and the particulates are likely to float in the atmosphere and to be taken into human bodies by breathing. In addition, it has been made obvious that carcinogens such as benzopyrene are contained in the particulates, and an adverse effect on the human bodies has become a large problem. Therefore, emission regulation for the particulates emitted from the diesel engine has been strengthened. Moreover, following such strengthening of the regulation, an exhaust gas purifying material capable of efficiently removing the particulates has been desired.
In recent years, as one of methods of removing the particulates, there has been known a method of using heat-resistant exhaust gas purifying filters such as a sealed ceramic honeycomb, ceramic foam, and metal foam, which are formed of three-dimensional structural supports. In this method, first, the particulates in the exhaust gas are collected. Then, after a back pressure rises, the exhaust gas purifying filters are heated by a burner, an electric heater, or the like, and the accumulated particulates are burned to be converted into carbon dioxide gas. Then, the carbon dioxide gas is emitted to the outside, and the filters are regenerated. These filters are filters of a surface collection type, which collect the particulates only on surfaces thereof. However, such a method has had a problem that a burning temperature of the particulates is high, resulting in that a large amount of energy is required to burn and remove the collected particulates and to regenerate the filters. Moreover, the method has had a problem that the filters are fused down and broken owing to combustion of the particulates in a high-temperature range and to reaction heat of the combustion. Moreover, since a special apparatus becomes necessary, the method has had a problem that a size and cost of the filters as purifying apparatuses are increased.
Meanwhile, there is a method, in which a catalyst is supported on the filter, the particulates are burned by a catalytic reaction, and the filter is burned and regenerated by heat of the exhaust gas without using the heater or the like. For Example, there have been proposed a particulate removing catalyst, in which a catalyst layer is coated on the filter, and the particulates are treated by a catalytic function, and proposed a manufacturing method of the particulate removing catalyst (refer to Japanese Patent Unexamined Publication No. 2002-102621).